The present invention relates to expansion valves of the type employed for controlling flow of refrigerant in refrigeration and air conditioning systems. Typically, in an air conditioning system, such as those employed for automotive passenger compartment cooling, an expansion valve throttles the flow of pressurized liquid refrigerant flowing from the condenser at relatively high pressures to provide relatively low pressure flow to an evaporator for heat absorption and return therefrom to the compressor inlet. In particular, expansion valves employed for controlling flow of liquid refrigerant to an evaporator in an automotive air conditioning system are of the type known as a "block" valve, wherein the valve body or block has a separate return flow passage provided therethrough in which vaporized refrigerant discharged from the evaporator flows to permit heat transfer therewith for control purposes.
Examples of such block type thermal expansion valves for automotive air conditioning use are those shown and described in U.S. Pat. No. 4,542,852, U.S. Pat. No. 5,269,459 and U.S. Pat. No. 5,547,126.
Heretofore, known thermal expansion valves have employed an actuator rod mechanism for moving a valve member and to expose the rod mechanism to the refrigerant flowing in the return passage to the compressor for heat transfer therebetween. It is also known to employ heat transfer through the rod to provide a temperature signal which in turn operates a pressure responsive means connected to the actuator rod mechanism for controlling the function of the expansion valve in response to changes in the temperature of the refrigerant discharging from the evaporator.
It is also known to provide a fluid filled chamber having pressurized fluid therein which acts upon a diaphragm as the pressure responsive means to move the valve actuator rod mechanism. It is also known to have a portion of the rod filled with the pressurized fluid to thereby be in heat transfer relationship with the refrigerant flowing through the return passage to the compressor inlet.
Such known thermal expansion block valves employed for automotive air conditioning applications have required precision machining of surfaces in the block for providing the build up or assembly of the valve on the block and provide accurate controlling of the valving action. Typically, the passages, ports and particularly the valve seat in the block have necessitated costly set up and machining operations from opposite ends of the block and have resulted in relatively high manufacturing costs for valves employed in high volume automotive applications. Furthermore, it has been required to completely assembly the valve components on the block in order to perform calibration and testing of the valve. This has resulted in costly assembly and testing operations and has prevented the detection of defective parts or assembly until the entire valve has been fully assembled.
Furthermore, the construction of known thermal expansion block valves has required expensive machine set ups for controlling the tolerances and location of the surfaces in the block for assembly of the valve components. Known block type thermal expansion valves for automotive air conditioning applications utilize an aluminum block which required that the machining operations be performed prior to application of anodic coating and thus precludes continuous manufacturing operations from the machining of the block to a final assembly and testing of the valve.
It has, therefore, long been desired to provide a way or means of providing a thermally responsive expansive valve for control of refrigerant in a refrigeration or air conditioning system such that the operating components of the valve may be assembled and calibrated prior to final assembly. It has also been desired to provide a thermally responsive expansion valve of the block type in a manner which minimizes the need for tight tolerance control of the location and machining of the valving surfaces in the block and which may be machined in a single set up and assembled in a continuous process.